1. Field of the Invention
The present invention relates to electronic circuits, and more particularly, to a voltage level shifter circuit.
2. Description of the Prior Art
Developments of Complementary Metal-Oxide-Semiconductor (CMOS) technology is rapidly performed, sizes of transistors are continuously shrunk to reduce chip areas, and thereby operating speed increases and power consumption can be saved. However, while the sizes of the transistors are continuously shrunk, gate oxides and transistor channels are continuously shrunk as well, allowable voltage difference between any two terminals of electrodes of the transistors (e.g. gate, drain, source and bulk/body) is reduced. When a voltage difference between any two terminals of a transistor exceeds a nominal voltage, the transistor may be damaged. Since the nominal voltage of advanced CMOS process is getting lower, conventional CMOS voltage level shifter circuit may have problems such as power source voltage being higher than the nominal voltage, which may damage the transistors.